The objective of this study will be to determine the applicability of correlating serum angiotensin converting enzyme (ACE) activity with acute lung damage. Rodent, non-human primate, dog and human will be studied. The former will be exposed to a number of lung toxicants. ACE activity will be measured in lung and serum. The relationship between ACE and lung injury of various etiologies can then be determined. Consenting human subjects in the intensive care unit at Sacramento Medical Center suffering from acute respiratory distress syndrome (ARDS) will also be examined. Their sera will have ACE measured and this parameter will be related to other indices of pulmonary function (radiographic, pulmonary function tests).